Various impurities, such as minerals and chlorine, often affect the taste, odor and appearance of tap water. In order to remove such impurities, filters are commonly coupled to household water faucets. Such filters typically include a housing for containing a filter and couplings for attaching the filter element into the water stream.
One such variety of this type of filter is described in U.S. Pat. No. 3,853,761, issued Dec. 10, 1978, to Robert M. McClory for a "Filter." The filter described in this patent includes a replaceable water filter cartridge and means for bypassing the cartridge when water purification is not required. The filter is attached to an existing water faucet merely by turning a coupling wheel to lock the filter onto the water spout. The cartridge is contained within a housing and may be removed or replaced merely by unscrewing the housing to expose the cartridge. A deflection mechanism is provided to select flow paths either through the filter cartridge or bypassing the cartridge.
The filter cartridge disclosed in the aforementioned patent is generally tubular and may be formed of any well known filtering material such as activated charcoal. The exterior surface of the filter cartridge is located in spaced relation to the housing wall, while the inside of the tubular cartridge is aligned over the unit's water outlet. Water is filtered by passing it through the tubular wall of the cartridge from the space between the cartridge and the housing toward the outlet. The aforementioned patent also indicates that a perforated tubular support core may be disposed adjacent the inner surface of the cartridge to support the filter against inwardly directed water pressure.
While the filter and cartridge device just described is adequate for some water purification jobs the filter is not especially efficient for use with those water supplies which contain large quantities of impurities. The primary reason is that the filtering path is very small, i.e. the centripital thickness of the filter cartridge. An improved filter cartridge which provides more efficient filtering would be a significant advance in the technology.